Distributed voltage regulation using Volt-Var controls of a smart PV inverter in a smart grid: An experimental study

Distributed photovoltaic (PV) generator systems (especially rooftop PV) have been increasing significantly in electrical power systems. However, due to the variability of their output power, it is challenging to integrate large number of these PV generator systems into the existing electrical grid. These distributed PV generator systems can cause large voltage fluctuations due to the oscillation in their power output and reverse power flow in highly penetrated areas. While real power curtailment is an option to manage voltage issues, it reduces the production of this clean energy and is governed by policies and contracts. Traditionally, the use of reactive power to control voltage on a power grid is done through maintaining the voltage within a tolerable range by using transformer tap-changers (TPC), capacitor banks (CB), voltage regulators (VR), static synchronous compensator (STATCOM), and static Var compensators (SVC). Installation and maintenance costs of these devices can be quite high and some have relatively slow response times on the order of many seconds. A smart PV inverter can help regulate voltage by absorbing and injecting reactive power (Var) to/from the grid by using the Volt-Var control function. This paper presents an experimental analysis of the inverter Volt-Var control method for voltage regulation. The capacitive (i.e., Var injection) and inductive (i.e., Var absorption) effects of using a smart inverter and its ability to influence the voltage at the distribution level is investigated in this paper. When the smart PV inverter injects reactive power, it increases the distribution voltage. Conversely, voltage is reduced when the smart inverter absorbs reactive power. As a result, electric power utilities can control the distribution voltage without installing additional devices on the power network. The analyses from a field deployment under the Maui Advanced Solar Initiative Project in Hawaii is discussed here. (C) 2018 Elsevier Ltd. All rights reserved.